Poly(vinyl alcohol) was employed for the preparation of hemodialysis membranes with and without the addition of acetic acid and poly(ethylene glycol) with the phase-inversion process. Aqueous solutions of sodium sulfate and sodium hydroxide were chosen as coagulant baths. The performances of the membranes were estimated by the measurement of the removal of uremic toxins (urea, uric acid, and creatinine) from human blood serum. The morphologies of the membranes were investigated and correlated to the membrane performance. Increasing the poly(ethylene glycol) concentration in the polymer solutions resulted in porous, spongelike structures because of the higher polarity of the polymer solutions and the enhancement of the diffusion rate of the nonsolvent (sodium sulfate and sodium hydroxide) into the polymer solutions. The porous structures of the membranes enhanced the removal of uremic toxins. The presence of acetic acid, with greater ionization strength, resulted in higher electrostatic interactions between positive and negative ions in the coagulation baths and polymer solutions. (c) 2007 Wiley Periodicals, Inc.